The sport of mountain climbing frequently requires the climber to ascend fixed lines or safety ropes in a variety of situations. These situations particularly include crevasse rescue during a glacier climb where the climber falls into a crevasse and is supported by his or her safety rope. The safety rope is attached to each climber and in turn secures the climbers together at spaced intervals along its length. The climber must then use a prusiking technique to ascend the rope to safety. In addition, the need to ascend a suspended rope is often encountered by construction workers, sailors, window washers and the like.
Many apparatuses have been developed for allowing the alpinist to ascend a suspended rope wherein the apparatus is permitted free relative upward sliding travel along the rope a but that sliding movement of the apparatus in the opposite or downward direction on the rope is prevented and the weight of the alpinist is supported at the present position when a downward load is applied to the apparatus.
Particularly in glacier travel as briefly discussed above, one or more members of a climbing team roped together by the safety rope will sometimes slip and fall into a crevasse, requiring the assistance of his fellow climbers to perform an ice axe arrest to stop the climber's fall. In ascending from the crevasse, the fallen climber has typically relied on the use of what is known as a prusik line. The prusik line is secured at one end to the safety rope with a prusik knot while the other end forms a loop within which the climber may insert his foot. A pair of prusik lines are used wherin each prusik line may then be alternately slid upwardly along the rope allowing the climber to gain elevation whereby the knot adaptably resists downward sliding movement when a load of the weight of the climber is applied to the loop. There are many disadvantages with the prusik, particularly the inefficiency of this system when the safety rope and prusik line become frozen and covered with ice. A need remained for a device to serve as an improved substitute for the prusik which the climber could easily attach to the safety rope in crevasse rescue situations.
The device which has become well known in the sport is the spring loaded ascender of Gibbs, U.S. Pat. No. 4,235,3218, 1981. Gibbs' ascender comprises a spring loaded brake lever which is pivotally mounted at one end to a housing, through which a rope is inserted. The brake lever is adapted to function as a camming device, applying frictional forces against the rope when a downward load is applied to the brake lever. The ascender may be slidingly moved upward along the rope with the actuating spring maintaining constant pressure of the brake against the rope. Downward movement of the ascender along the rope is prevented when the downward load created by a climber's weight is applied to the brake lever.
The Gibbs invention and others, such as that of Hoffman, U.S. Pat. No. 3,814,210, 1975, have been developed primarily to allow the climber ascend a fixed rope which is suspended from a higher elevation. The climber may actually use these ascending devices to pull his or her own weight up the rope or may simply use the device, typically called an ascender, as a safety clamp to support this weight and maintain present position on the rope in case of a fall.
Similar equipment has been developed primarily for use as a braking apparatus, such as would be used in rappelling on a fixed or suspended rope or other activity when a person desires to control and reduce the speed of descending a rope using an aid. Wagner, U.S. Pat. No. 4,019,609, has developed a brake apparatus for use in rappelling wherein a brake bar is utilized in connection with two or more carabiners. A length of webbing is secured to the climber at one end and to the carabiners at the other. The rope used in the descent is then adaptably threaded through the carabiners and around the brake bar in such a fashion that the apparatus applies frictional forces to the rope as he climber begins the descent. Frictional forces allow the brake apparatus to travel down along the rope yet at reduced speed.
Despite the development of various braking and ascending equipment, there remains a need for climbers to have a simple and dependable apparatus which will allow safe ascent of a safety rope in a rescue situation or permit the climber to be able to ascend a fixed rope while climbing an ice wall or rock pitch, for example. In contrast to the inventions of Gibbs and others, an additional requirement was to provide an ascending apparatus that was not comprised of mechanical moving parts such as springs or cams which would require maintenance or could freeze or ice up or fail during use. A very light, single handed, manually operable apparatus was needed which would allow upward travel along the rope and prevent any downward movement once a load was applied.
Rappelling equipment, such as the inventions of Wagner and Stephen, have included standard carabiners in combination with a braking means. There remained a need, however, for an ascender which would utilize existing directly bear against a climbing rope to hold a climber at his or her selected elevation along the rope, rather than simply control the speed of movement along the rope and merely slow descent on the rope as Wagner and Stephens' inventions were designed to do.